<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title></title>

	<style>
		.box{
			width: 300px;
			height: 300px;
			background-color: red;
			/*float: left;*/
		}
		.child{
			width: 100px;
			height: 100px;
			background-color: green;
			margin-left: 50px;
			margin-top: 50px;
		}
	</style>
</head>
<body>
	<div class="box">
		<div class="child"></div>
	</div>
</body>
</html>